Pooltester, Checkits and Poolcheck tablets

DPD reagents are a colorimetric method based on N-diethyl-p-phenylenediamine which, when in contact with the water sample, will react to turn magenta in proportion to the concentration of chlorine present in the water.
DPD reagents are white in color and crystalline in appearance.
When a reagent (tablet or powder) is not white and has a grayish/brownish color, this reagent should not be used.